(a) Field of the Invention
The present invention relates to a display panel including a plurality of signal line, and particularly to a liquid crystal display including a plurality of lines having different length.
(b) Description of Related Art
A display device such as a liquid crystal display (LCD) or an organic electroluminescence (EL) display includes a plurality of pixels as basic elements for displaying an image. Each pixel includes a switching element for independent operation.
The switching elements include a tri-terminal element including a control terminal, an input terminal, and an output terminal, which is turned on or off in response to a signal applied to the control terminal and selectively transmits a signal entering into the input terminal via the output terminal. For this purpose, a plurality of signal lines for applying the signals to the control terminals and the input terminals of the switching elements and a plurality of driving circuits for supplying the signals to the signal lines are provided at a display device.
The TFT array panel includes a plurality of scanning signal lines or gate lines for transmitting scanning signals, a plurality of image signal lines or data lines for transmitting image signals, a plurality of TFTs connected to the gate lines and the data lines, a plurality of pixel electrodes connected to the TFTs, a gate insulating layer covering the gate lines for insulation, and a passivation layer covering the TFTs and the data lines for insulation.
The TFT includes a gate electrode, which is a part of the gate line, a semiconductor layer for a channel, source and drain electrode, which are parts of the data line, a gate insulating layer, and a passivation layer. The TFT is a switching element for transmitting or blocking the image signal from the data line to the pixel electrode in response to the scanning signal from the gate line.
The driving circuits are located near edges of the display device and connected to end portions of the signal lines, which are clustered in a small area (referred to as “connection area” hereinafter) for the connection. On the contrary, the distances between the signal lines in an area (referred to as “display area”) including the pixels have a value determined by the size of the pixels to have larger values than the distances between their end portions connected to the driving circuits. Accordingly, a plurality of fan-out areas in which the distances between the signal lines gradually increase or decrease like a fan are provided between the connection area and the display area.
Although the signal lines near the center of the fan-out area extends straight without curving, the signal lines closer to edges of the fan-out area have larger curving angles. This configuration of the fan-out area results in the difference in the length between the signal lines such that the line length near the center of the fan-out area is shorter than the line length near the edges of the fan-out area. The length difference differentiates the resistances of the signal lines, which results in the deteriorated image quality.
In particular, since a liquid crystal display uses a voltage control scheme which controls voltages applied to the pixels, the voltage difference due to the resistance difference causes a severe problem in image quality.